Add MIT license to LinearSolveAutotune and update auth docs

[ChrisRackauckas-Claude]

Summary

• Added MIT LICENSE file to the LinearSolveAutotune sublibrary
• Updated documentation to reflect new authentication features introduced in recent PRs
• Improved user experience documentation for the automatic authentication flow

Changes

License Addition

• Added standard MIT LICENSE file to lib/LinearSolveAutotune/ directory
• Ensures the sublibrary has proper licensing information

Documentation Updates in docs/src/tutorials/autotune.md

• New "Automatic Authentication" section: Documents the new automatic authentication prompt feature that helps users set up GitHub authentication interactively
• Updated authentication instructions: Clarifies that gh CLI is now optional since LinearSolveAutotune includes gh_cli_jll as a fallback
• Added usage examples: Shows how to use the auto_login parameter in share_results()
• Improved clarity: Explains the authentication flow is now more user-friendly with automatic prompts

Context

This PR complements the recent authentication improvements:

• PR Add gh_cli_jll as fallback for LinearSolveAutotune when gh CLI is not installed #687: Added gh_cli_jll as a fallback for systems without gh installed
• PR Add automatic gh auth login prompt when sharing benchmark results #689: Added automatic authentication prompts when sharing results

The documentation now accurately reflects these improvements, making it clear that users no longer need to manually install gh CLI or set up authentication before using the telemetry features.

Test plan

• Documentation builds successfully
• LICENSE file is properly formatted
• Documentation accurately reflects the current authentication behavior

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